Producing coke from hydrotreated crude oil

ABSTRACT

D R A W I N G WHOLE SOUR CRUDE OIL TOGETHER WITH C5-PLUS LIQUID PRODUCTS FROM A COKER ARE HUDROTREATED PRIOR TO SEPARATION INTO VARIOUS BOILING-RANGE PRODUCTS. THE RESIDUAL MATERIAL FROM THIS DISTILLATION IS COKED TO OBTAIN LOW SULFUR COKE AND LIQUID PRODUCTS OF WHICH THE C5-PLUS PORTION IS RECYCLED TO COMMINGLE WITH THE CRUDE OIL PRIOR TO HYDROTREATING. OPTIONALLY, THE CRUDE OIL MAY BE TOPPED TO REMOVE FRACTIONS BOILING IN THE RANGE OF FROM THE INITIAL BOILING POINT OF THE CRUDE TO ABOUT 400*F., PRIOR TO HYDROTREATING.

Nov. 27, 1973 A. H. PETERSON ETAL 3,7752% PRODUCING COKE FROM HYDROTREATED CRUDE OIL Filed June 28, 1971 2 Sheets-Sheet 1 smuaem '0 ll l2 l3 2 05mm? A-i1 FURNACE HYDROT/PEATER --'---&I-

----0 2s 22 MAW/V 22 COLUMN/57 w com? l/WE/VTORS ALA/V l1. PETERSON 2 FRANK L. OUR/WSW TTO/P/VEV United States Patent O 3,775,294 PRODUCING COKE FROM 'HYDROTREATED CRUDE OIL Alan H. Peterson, Littleton, and Frank L. Dormish, Denver, Colo., assignors to Marathon Oil Company, Findlay, Ohio Filed June 28, 1971, Ser. No. 157,529

Int. Cl. Clog 37/00 U.S. Cl. 208-89 Claims ABSTRACT OF THE DISCLOSURE CROSS REFERENCES TO RELATED APPLICATIONS The following U.S. patent applications relate to the general field of the invention: Ser. No. 157,528, filed June 28, 1971, and Ser. No. 770,724, filed Oct. 25, 1968, now abandoned and Ser. No. 771,248, filed Oct. 28, 1968, now Pat. No. 3,594,309 (both of which are priority documents for published Netherlands patents).

BACKGROUND OF THE INVENTION Field of the invention The present invention relates generally to the field of hydrocarbon conversion processes and more specifically to hydrotreating and coking generally classified in the United States Patent Oflice, Class 208 subclass 212.

Description of the prior art A search in the United States Patent Office has located the following prior art: U.S. 2,888,393 in which coking is carried out in the presence of added hydrogen (which the invention does not use) and the products are hydrotreated. No hydrotreatment of whole crude is involved; U.S. 2,871,182 in which coker feedstock boiling above 600 F. is hydrotreated and cracked products boiling above gasoline may be returned to the hydrotreater. Whole crude oil is not mentioned as a feedstock; U.S. 3,238,117 in which crude oil is coked (without prior hydrotreating) and the entire product therefrom is hydrocracked (not hydrotreated) with further upgrading by reforming; U.S. Pat. 3,072,570 which cokes residual oils then hydrocracks the resulting coker gas oil. No hydrotreatment of whole crude with any coker product other than gas oil is involved; U.S. Pat. 2,988,501 which does hydrotreat crude oils (particularly shale oil, etc.) in the presence of recycled material after removal of asphaltenes by precipitation. The present invention does not recycle (directly) or separate asphaltenes; U.S. Pat. 2,987,467 which hydrotreats heavy oils in two stages: first, without a hydrogenation catalyst under conditions providing significant cracking, and then, with a hydrotreating catalyst. No mention of whole crude and no combining of cracked products with whole crude are involved. Feed stocks are residual oils in every case; U.S. Pat. 2,006,199 which does not mention hydrotreatment of whole crude but does hydrotreat asphaltenes which may be derived from crude by distillation and/or thermal cracking; other hydrocarbon conversion processes are taught by the following U.S. Pats. 3,008,895; 2,895,896; 2,813,824; 2,614,067; and 2,007,378.

3,775,294 Patented Nov. 27, 1973 Hydrotreating of petroleum residual is taught by the following: Netherlands patent NL-6916 218-Q which claims priority of U.S. patent application 771,248, filed Oct. 28, 1968, teaches processes for converting sulfurous, hydrocarbonaceous black oils into lower boiling, normally liquid-hydrocarbon products of reduced sulfur content with an integrated process involving cracking in the presence of hydrogen and fixed bed catalytic desulfurization. Netherlands patent NL-6916 017-Q which claims priority of U.S. patent application Ser. No. 770,724, filed Oct. 25, 1968, teaches hydrodesulfurization of crude oil or reduced crude containing asphaltene fractions at low temperatures in the presence of a Group VI/ Group VII metal catalyst on alumina.

Of the above references, only U.S. Pat. 2,988,501, which cokes an asphaltene phase (see its column 3, lines 63-67), involves the hydrotreating of whole crude.

SUMMARY OF THE INVENTION General statement of the invention According to the present invention, whole crude is hydrotreated, then fractionated and the residual oils are coked to produce coke and liquid products, whereupon the liquid products are recycled back to the crude oil feed prior to the hydrotreating step. The advantages of the invention include: capital cost saving by reducing number of fractionating columns and number of hydrotreating units required; reduced quantities of coke and corresponding increases in quantities of more valuable liquid products; lower sulfur content in the coke, in the C and lighter overheads and in all other liquid products; reduced corrosion due to sulfur removal before contact with crude tower, coker and subsequent downstream processing units; high throughput through the hydrotreater (the light fractions are hydrotreated in a unit no larger than that required for conventional hydrotreating of the heavier fractions only); and lower olefin contents in naphtha products, particularly gasoline.

Utility of the invention The present invention provides coke, particularly low sulfur coke which is of special value in the production of electrodes, e.g., for the electrolytic production of aluminum, and also produces low-sulfur liquid products which can be refined into naphthas, particularly gasoline having lower olefin contents.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of a refinery system hydrotreating whole crude oil of the present invention.

FIG. 2 shows a schematic diagram of a process for hydrotreating topped crude oil according to the invention.

DESCRIPTION OF THE PREFERRED- EMBODIMENTS Starting materials Hydrocarbons: It is an important aspect of the present invention that whole crude oil is hydrotreated. Previous processes have hydrotreated residual, e.g., 650 F. plus portions without achieving the advantages of the present invention as is demonstrated by a comparison of Examples HI and V. Crudes which are partially useful for the practice of the invention are those which are relatively high in sulfur content but low in asphaltene and heavy metals content. Sour West Texas crude is a good example of this type of crude.

Topped crudes, e.g., those having the portion boiling below about 400 F. fractioned out, can be utilized in place of the whole crude oil.

Residual fraction: the preferred residual fraction for coking according to the present invention is the fraction generally boiling above about 900 F., more preferably above about 1000 F., and most preferably above about 1050 F.

Coker liquid products: the coker liquid products selected for recycle will generally consist of the entire liquid product from C or C up through the highest boiling liquid products produced. The lower molecular weight material, particularly the C C and perhaps C portion are advantageously separated for olefin recovery. Any other portions of the coker liquid product may also be separated for separate use, if desired. From about 1 to about 100, more preferably from 50 to about 100, and most preferably from 75 to about 100 volume percent of liquid (C -plus) products from the coker will be mixed with the whole crude entering the hydrotreating process. The remaining coker liquids, if any, can be utilized for conventional purposes, e.g., for gasoline and heavier fuels.

Hydrogen: the hydrogen utilized with the present invention can be of commercial purity such as that derived from the reforming of naphtha as by any of the reforming processes described on pp. 184-193 of the September 1970 issue of Hydrocarbon Processing or can be manufactured specially for the purpose such as by steam reforming or partial oxidation of hydrocarbons (ibid. pp. 269-270). From about 1000 to about 6000, more preferably about 2000 to about 5000, and most preferably from about 2500 to about 4000 standard cubic feet of hydrogen will be contacted with each barrel of crude oil.

Catalyst: A wide variety of hydrogenation catalysts, especially those containing metals selected from the group nickel, molybdenum, cobalt and tungsten, or compounds containing such metals, can be employed including those marketed by the Girdler Division of Chemetron Corp. under the trade name Girdler G-51, Girdler G-76; those marketed by Union Oil Company of California under the trade name N-12; those marketed by American Cyanamid Company under the trade name Cyanamid HDS-ZA and Cyanamid EDS-1450, Cyanamid HTS- 1441, Cyanamid HDS-9A, and Cyanamid HDS-BA; those marketed by the Davison Chemical Company, Division of W. R. Grace & Co. under the trade name Davison-HDS and that marketed by Nalco Chemical Company under the trade name Nalco NM-SOZ and that marketed by Catalyst and Chemicals, Inc. under the trade name CCI C-20-07. Of these, nickel-molybdenum catalysts, e.g., American Cyanamid HDS-3, EDS-9A and Nalco NM-502 are most preferred.

Catalyst support: The preferred catalyst supports are alumina, silica, magnesia or combinations thereof. In general, the support should not be sufficiently acidic so as to cause extensive hydrocracking of the oil under the preferred reaction conditions. For use in a fixed-bed hydrotreating unit a catalyst in the form of an extrudate, pellet or sphere of such size as to avoid excessive pressure drop through the catalyst bed but small enough to provide good transport of the oil into the center of the catalyst particle is used. Sizes from about /s to 1 inch are generally preferred. In a moving or ebulating bed hydrotreating reactor, inch or smaller extrudates or other shaped particles can be used to advantage.

Temperature; While not narrowly critical, the temperature during the hydrotreating reaction should be from 600 to about 850 F., more preferably from 650 to about 800 F., and most preferably from 675 to about 775 F. The temperature used will depend on the relative hydrodesulfurization and hydrocracking activities of the particular catalyst used and will normally be increased during a run to compensate for catalyst deactivation.

Pressure: While also not narrowly critical, pressure during the hydrotreating reaction should be from about 250 to about 5000, more preferably from about 600 to about 2500 and most preferably from 800 to about 2000 p.s.1.g.

Liquid hourly space velocity: The liquid hourly space velocity will generally be in the range of from about 4 0.5 to about 6, more preferably 0.5 to about 4, and most preferably 1 to about 3 volumes of liquid per volume of hydrotreating catalyst per hour.

Coking: The coking is carried out under conventional conditions, e.g., those described on pages -181 of the September 1970 issue of Hydrocarbon Processing and in the references therein.

Apparatus: Conventional hydrotreating, distillation and coking apparatus can be employed. Though not necessary to the invention, with crude having high content of metals and/ or particulates, a conventional guard case filled with inexpensive catalyst can be provided upstream of the main hydrotreating reactor to protect the more expensive main catalyst.

Examples: Examples I, IV and V are according to the invention. Examples II and III are comparative examples to illustrate the loss of advantages when the crude oil is first fractionated and the fractions separately hydrotreated.

EXAMPLE I (Hydrotreating whole crude according to the invention) Referring to FIG. 1, whole crude 10 enters the desalter 11 of conventional design which removes inorganic halides. The desalted crude is heatcd in heat exchanger 12, contacted with make-up hydrogen 14 and recycle hydrogen 33 and further heated in furnace 13. The hot crude plus hydrogen stream is passed over a bed of nickel-molybdenum catalyst in hydrotreater 15 where hydrotreating occurs. The hydrotreated stream is cooled in heat exchanger 16 and fed to separator 17 which separates the gaseous from the liquid products. The liquid products are fed to the main distillation columns 18 where they are fractionated into product streams; gas 19 (composed primarily of C through 0.; which is sent to a conventional gas concentration facility), gasoline 20 (composed primarily of C through C fractions boiling up to about 400 F. and which is sent to blending and/or catalytic reforming). middle distillate 21 (which may be more than one fraction and which is composed primarily of kerosene, diesel fuel, and jet fuel) gas oil 22 (both atmospheric and vacuum gas oil which is sent to catalytic cracking or to hydrocracking and residuals 23 which are sent to conventional delayed coker 24 to produce coke 25). (A conventional fluid coker could be used in place of the delayed coker 24.) Overhead from the coker is sent to heat exchanger 26 where it is cooled before fractionation in fractionating column 27. Overhead 28 from column 27 is composed primarily of C and lighter hydrocarbons and is sent to gas concentration. The bottoms 29 from fractionating tower 27 are composed primarily of C and heavier hydrocarbons and are recycled back to mix with the efiluent from desalter 11. The gaseous efiluent 30 from separator 17 is sent to scrubber 31 which removes a stream 32 consisting primarily of hydrogen sulfide and ammonia. The remainder of the efiluent from scrubber 31 consists primarily of hydrogen 33 which is recycled to mix with the make-up hydrogen and liquid feed to the hydrotreater 15. Light hydrocarbons are vented from the scrubber 31 as necessary to prevent excesive dilution of the recycled hydrogen. In this example the total hydrogen (make-up plus recycle) is about 3350 standard cubic feet per barrel of total oil (crude plus recycle). This and other particulars are given in the data below.

A crude oil containing 1.67 weight percent sulfur is processed according to this invention as shown in FIG. 1, to yield low sulfur liquid products and a delayed coke of reduced sulfur content. The sulfur contents of various fractions of the raw crude oil are shown in the table below.

5 The hydrotreater 15 is operatedat 700 C. and 1500 p.s.i.g. with a total hydrogen feed of 3350 standard cubic feet per barrel of. oil. The oil is fed at a liquid hourly space velocity of 1.7 hr." The catalyst used is American Cyanamid HDS-3A. h The feed to thecoking unit 24consists of residual boiling-iabove about 975 F. from column 18. The delayed coking unit 24 is Operated at a 925 F. bed temperature .and inlet feed temperature of 1000 F. The oil to steam feedratio is 20.5 volume of oil to volume of water. Cokingtime is 9 hours. I

' Yields of products based upon crude oil charge rate of 1000 barrels per day are tabulated below.

Yield per Weight 1,000 bbl. percent Product crude sulfur Dry gas 4 3,3401h Propane and propylene 12.4 bbl Butanes and b n 8.2 bbl. 015-400 F. gasoline bbl 400-600 F. middle disti1late..-- GOO-975 F. gas oil 4 COktL.-.

The total charge to the hydrotreating unit 15 is 1185 bbl. per day. The additional charge rate of 185 bbl. per day is the recycled coker condensate 29.

EXAMPLE II V .(Conventionally fractionating and coking without hydrotreating) The same crude oil used in Example I is conventionally distilled and the residual fraction is coked under the conditions of Example I. Yields and sulfur contents of the products are tabulated below.

Yield per Weight 1,000 bbl. percent Product crude sulfur Dry mas 4,776 lb Propane and propylene 11.5 bbl Butanes and hurenes 6.7 bbL. 05-400 F. gasoline. 276 bbl- GOO-975 F. gas oil Coke Total liquid products EXAMPLE III (Conventional hydrotreating of atmospheric residual) The atmospheric residual boiling above 630 F. from the raw crude oil of Example I is conventionally hydrotreated at 725 F., 1500 p.s.i.g. and a liquid hourly space velocity of 0.9 hr. using Union N-21 catalyst. Sulfur contents of the resulting product fractions are shown in the table below. Only small amounts of products boiling below 600 F. are obtained.

Ex. III Ex.IV Ex.V

Fraction of crude hydrotreated, F 630+ 400+ LHSV, entire feed 0. 9 1. 2 1. 9 LHSIY, 630 Fi-l-upfortion of igedifr. .t O. 9 0.9 1. l Wei t ercen s ur in pro nc ac ions:

500 s. end point 0. 01 0. 01 0. 01 400-600 F 0. 01 0. 01 0. 01 6004.050 F 0. 09 0. 06 0. 09 1,050 F. initial 18.? 0. 58 0. 43 0. 41

- 1 Whole crude.-

6 EXAMPLE IV Referring to FIG. 2. all elements shown with figures below 40 are identical with those previously described for FIG. 1. The heat exchanger 26 and fractionator 27 located on the eflluent from the coker in FIG. 1 have been deleted. The fractionating column 40 tops the oil prior to hydrogenation to remove a naphtha stream 41, boiling below about 400 F. The topped crude 42 is then mixed with the make-up hydrogen 14 and the recycled hydrogen 33 as described in FIG. 1. The overhead 43 from the coker 24 is recycled directly back to mixing with the desalted whole crude.

The portion of the crude oil of Example I boiling above 400 F. is hydrotreated over the catalyst of Example III under substantially identical conditions except that the liquid hourly space velocity of the total feed is increased such that the space velocity of just the 630 F. plus portion of the feed is substantially the same as in Example 111. The lower sulfur contents of the 600-l050 F. and residual (1050 F. plus) fractions of the product of Example IV show the advantage of processing the. 400-600 F. portion of the crude oil together with the atmospheric residual (630 F. plus) fraction. No increase in hydrotreating reactor size is required since the space velocity can be increased sufficiently to include this additional material and still obtain improved desulfurization of the residual. Only a small amount of product boiling below 400 F. is obtained.

EXAMPLE V (Demonstrating the advantages of hydrotreating whole crude oil as opposed to atmospheric residual) The whole crude oil of Example I is hydrotreated under essentially identical conditions as in Example IH, except that the liquid hourly space velocity of the total feed is increased sufficiently that more of the 630 F. plus portion of the crude oil is being hydrotreated per day than in Example III using the same size reactor. The sulfur content of all of the product fractions is equal to or lower than the corresponding products of Example HI despite the processing of both the lighter portion of the crude and a somewhat greater amount per day of 630 F. plus atmospheric residual.

Modifications of the invention It should be understood that the invention is capable of a variety of modifications and variations which will be made apparent to those skilled in the art by a reading of the specification and which are to be included within the spirit of the claims appended hereto.

What is claimed is:

1. In a process for the manufacture of coke from residues derived from the fractionation of crude oil, the improvement comprising:

(a) hydrotreating whole crude oil or crude oil topped to about 400 F. prior to said fractionation which produces said residues, said hydrotreating being accomplished by contacting said crude oil with from about 1000 to about 6000 standard cubic feet of hydrogen per barrel of crude oil at a temperature of from about 600 to about 850 F. and a pressure of from about 250 to about 5000 p.s.i.g. in the presence of a hydrotreating catalyst.

(b) fractionally distilling to produce gas oil and a residual high boiling fraction, and

(c) coking said residual high boiling fraction to obtain coke gaseous products and liquid products, and

(d) recycling substantially all C and heavier liquid products from said coker to mix with said crude oil prior to said hydrotreating.

2. A process according to claim 1 wherein the crude oil is topped to remove a fraction boiling below about 400 F. prior to said hydrotreating of said crude oil.

3. A process according to claim 1 wherein the crude oil is contacted with from about 2000 to about 5000 standard cubic feet of hydrogen per barrel of crude oil at a temperature of from about 650 to about 800 F. and at a pressure of from about 600 to about 2500 p.s.i.-g.

4. A process according to claim 1 wherein said hydrotreating catalyst comprises a metal selected from the group consisting of nickel, molybdenum, cobalt and tungsten or a compound containing one of the foregoing metals.

5. A process according to claim 4 wherein the crude oil is contacted with from about 2000 to about 5000 standard cubic feet of hydrogen per barrel of crude oil at a temperature of from about 650 to about 800 F. and at a pressure of from about 600 to about 2500 p.s.i.g.

6. A process according to claim 4 wherein the crude oil is topped to remove a fraction boiling below about 400 F. prior to said hydrotreating of said crude oil.

7. A process for the manufacture of coke and refined liquid hydrocarbons from whole crude or crude which has been topped to remove a fraction boiling below about 400 F., said process comprising in combination:

(a) desalting said crude as necessary to reduce the content of inorganic halides,

(b) contacting said crude with hydrogen to form a hot crude plus hydrogen stream,

() passing said hot crude plus hydrogen stream over a hydrotreating catalyst at a temperature of from about 675 to about 775 F. and at a pressure of from about 800 to about 2000 p.s.-i.g. and at a liquid hourly space velocity of from about 0.5 to about 4 volumes of liquid per volume of hydrotreating catalyst per hour to produce a hydrotreated product stream,

((1) fractionating said hydrotreated product stream to produce a plurality of refined liquid hydrocarbon products and a residual stream,

(e) coking substantially all of said residual stream in a coker to produce coke and coker overhead,

(f) fractionating said coker overhead to produce an overhead comprising C and lighter hydrocarbons and at least one higher boiling fraction comprising C and heavier hydrocarbons,

(g) recycling at least a portion of said higher boiling fraction from said fractionation of said coker overhead for mixing with said crude oil or topped crude being fed to said hydrotreater.

8. A process according to claim 7 wherein the feed to said hydrotreater consists essentially of whole crude oil, recycled bottoms from said fractionation of said coker overheads, and hydrogen.

9. A process according to claim 7 wherein the feed to said hydrotreater consists essentially of topped crude oil, recycle bottoms from said fractionation of said coker oT erheads, and hydrogen.

10. A process according to claim 1 wherein the material hydrotreated in step (a) can consist essentially of whole c rude oil.

References Cited UNITED STATES PATENTS 3,684,688 8/1972 Roselius 208 2,871,182 1/1959 Weekman 20850 2,963,416 12/1960 Ward et a1. 208-50 3,617,501 11/1971 Eng et al. 208--89 2,526,966 10/1950 Oberfell et al. 208-64 2,785,120 3/1957 Metcalf 208-88 HERBERT LEVINE, Primary Examiner U.S. Cl. X.R.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,775,294

Dated lnventofls) Alan H. Peterson et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 2, line 62: Delete "partially" and insert therefor --particularly.

Col. 5, line 1: Delete "700C" and insert Sixth Day of September 1977 [SEAL] A ttest:

RUTH C. MASON LUTRELLE F. PARKER Arresting Officer Acting Commissioner of Patents and Trademarks 

